A magnetic head and disk tester is an instrument that is used for testing the characteristics of magnetic heads and disks. Tester parameters may include signal-to-noise ratio, bit error rate, and the like. A tester typically includes two main assemblies, an electro-mechanical assembly that performs movements of a head with respect to a disk, and an electronic assembly that is responsible for measurements, calculations, and analysis of the measured data. The electro-mechanical assembly of the tester is known as a spinstand. The spinstand generally simulates the motions of the head with respect to the disk that occur in, for example, a hard disk drive. The spinstand includes a support and rotational driver for the magnetic disk. The spinstand also includes an assembly of components which effects movement and placement of a magnetic head relative to the rotating, or spinning, magnetic disk, often referred to as a head-loading mechanism. Since the magnetic head and disk are very fragile by their nature, it is important that the magnetic head and disk never actually come into physical contact during operation. However, the magnetic head and disk are positioned in extremely close proximity to each other under such conditions to support magnetic read and write operations. Therefore, precise placement of the magnetic head relative to the magnetic disk is essential to avoid damaging contact between the two.
In a typical spinstand configuration, the magnetic head is part of a head-gimbal assembly which disposes the magnetic head over the magnetic disk (but separated by aerodynamic forces) and is moved under the control of the head-loading mechanism. FIG. 1 shows a typical prior art head-gimbal assembly (HGA) 15, which includes a slider 10 disposed at a distal end of an elongated resilient suspension member 12 and a planar mounting portion 14 formed at its proximal end. Generally the suspension member 12 extends along a suspension axis S. The suspension axis S is angularly offset with respect to the planar portion 14. Slider 10 includes the magnetic head read and write elements of head-gimbal assembly 15. Disposed along the underside of suspension member 12, typically, are electrical wires 16 which carry read and write data signals to and from the magnetic head. In operation, the head-gimbal assembly 15 is secured to a cartridge, which in turn is secured to and manipulated by head-loading mechanism components to accomplish loading of the magnetic head over/onto the spinning magnetic disk.
To effect loading, the head-loading mechanism advances the slider toward a magnetic medium-bearing surface of the spinning disk. The resilience characteristic of the suspension is selected so that the slider is spring-biased toward the disk but kept separated form that disk due to air flow between the head and the spinning disk. The separation between the head and disk surface is referred to in art as the "flying height".
Thus, for the configuration of FIG. 1, suspension member 12 biases slider 10 toward the magnetic disk. When slider 10 is positioned near the spinning magnetic disk, an "air bearing" is formed between the slider 10 and the magnetic disk, and aerodynamic forces on the slider 10 counter the bias of the suspension member 12, causing the slider 10 to remain suspended just above the rotating magnetic disk, separated by a predetermined small gap (or "flying height") between slider 10 and the disk surface. The actual positioning of slider 10 relative to the magnetic disk, and the associated manipulation of the suspension member 12 are accomplished by various components of the head-loading mechanism. For example, in various prior art embodiments, arms or bars are used to control the suspension member 12 as the slider 10 is positioned near, or loaded onto, the disk.
In a typical prior art head-loading mechanism, the mounting portion 14 of head-gimbal assembly 15 is secured to a flat surface of a rigid block, known as a cartridge. The cartridge (with the head-gimbal assembly attached) is first affixed to a mating surface of the head-loading mechanism, for example using a pneumatic coupling. As part of the loading operation, the head-loading mechanism is then moved close to a magnetic disk and the slider 10 (and its read and write elements) is positioned over the disk such that the slider remains close to the disk, but is not brought into close proximity with the disk surface at this point. The disk may or may not be spinning during this part of the loading operation, depending on the particular design and configuration of the head and disk. The subsequent loading and testing operations depend on the type of head-loading mechanism incorporated by the spinstand of the tester. Those loading and test operations generally include lowering the head toward the disk to establish the suspension-air bearing force balance (i.e. the "loading") followed by moving the head through a series of predetermined test positions relative to the disk and reading and writing data (i.e. the "testing").
A portion of a prior art spinstand head-loading mechanism 20 is shown FIG. 2 as an example of such mechanisms. A head-gimbal assembly of the type shown in FIG. 1, and a cartridge 22 are mounted on a mating surface of the head loading mechanism 20 of the spinstand so that the slider 10 is opposite but grossly spaced apart, from the upper surface of spinning magnetic disk 26. The suspension member 12 is angled downward toward disk 26, with electrical wires 16 disposed on the underside of suspension member 12. The mounting portion 14 of the suspension member 12 is secured to the cartridge 22 which is secured in turn to head loading mechanism 20. In this exemplary prior art configuration, a metal arm 24 is disposed under the suspension member 12 such that its upper surface engages the underside of suspension member 12 between the slider 10 and portion 14, ensuring that slider 10 is significantly separated from disk 26. Arm 24 is movable in the X and Y directions, as illustrated in FIG. 2. In operation after the disk 26 is spinning, and with arm 24 in its extended position so that it underlies the suspension member 12, and with slider 10 positioned over disk 26 (all as shown in FIG. 2), arm 24 is lowered until slider 10 approaches its flying height and suspension member 12 separates from arm 24. Then arm 24 is retracted and testing begins. This prior art configuration has several significant problems. First during the loading operation, slider 10 moves on an arc and therefore the motion can be controlled more accurately and smoothly if arm 24 contacts suspension member 12 at a point close to slider 10. However, that is problematic because since suspension 12 is originally at an angle to mounting portion 14 of the head, arm 24 can not be positioned very close to slider 10, as this would cause arm 24 to contact and damage slider 10 as cartridge 22 (with the attached head-gimbal assembly) is installed on head loading mechanism 20. During installation of cartridge 22 on head loading unit 20, arm 24 remains in its position and therefore lifts suspension element 12 as cartridge 22 makes firm contact with head loading mechanism 20. Again, because suspension 12 is originally at an angle to mounting portion 14 of the head-gimbal assembly, and arm 24 is made of metal, this operation typically causes arm 24 to scratch the side of suspension 12 where it contacts arm 24. In some types of heads, this results in damage to electrical wires 16 underneath suspension 12.
Another form of prior art spinstand head-loading mechanism is shown in FIG. 3. In that configuration, a head cartridge is initially mounted to head loading mechanism 20. In this configuration, lift bar 24 (which has an inclined profile wedge at its distal end, and which is retractable in the X-direction) is positioned between slider 10 and the top surface of disk surface 26, where the thickness of the tapered tip of the wedge is less than the gap between suspension member 12 and disk surface 26 when the head is loaded on the disk. As a wedge is inserted between suspension member 12 and the disk 26, the slider 10 is lifted off of the disk 26, and as lift bar 24 is pulled away, slider 10 moves bar 24 closer to the disk, until it starts flying over surface of disk 26. There is a gap between bar 24 and disk surface 26 at all times in order to avoid contact between the two. Due to the high precision and small dimensions (especially thickness) of bar 24, it can not be manufactured of a plastic material. During installation of a cartridge 22 (with the attached head-gimbal assembly) on head loading mechanism 20, the wedge portion of arm 24 remains in its position and therefore lifts suspension member 12 as cartridge 22 makes firm contact with the mounting surface on head loading mechanism 20. Because suspension member 12 is originally at an angle to mounting portion 14 of the head-gimbal assembly, this operation can cause arm 24 to scratch the side of suspension member 12 where it contacts arm 24. In some types of heads, this results in damage to electrical wires 16 underneath suspension 12.
Another prior art head loading assembly is shown in FIG. 4. That assembly addresses the potential for damage to electrical wires 16 of the head-gimbal assembly. In that prior art assembly, load and unload operations are achieved by rotating a mounting block 43 (together with the head-gimbal assembly) with respect to cartridge 22, about an axis 44 parallel to the top surface of disk 26. There are no bars or wedges that contact the suspension during these operations. During loading operation, the head loading mechanism 20 is brought close to the disk 26 such that the slider, 10 remains over the disk, and mounting block 43 together with the head-gimbal assembly, is rotated until mounting portion 14 is parallel to the disk 26, at a specified distance from the surface of disk 26. During this rotation, due to the initial angle between suspension member 12 and mounting portion 14 of the head-gimbal assembly, slider 10 contacts the disk before mounting portion 14 becomes parallel to the disk 26, and therefore may cause scratches and pits on disk surface 26 an slider 10. During unloading operation, mounting block 43 is rotated in the opposite direction compared to the loading operation. As slider 10 is lifted off of the disk 26, suspension member 12 can vibrate vertically since it is not supported at a point close to slider 10. This may cause scratches and pits on surface 26 and slider 10.
In order to overcome some of the problems associated with the above described prior art head loading assemblies, more recent prior art suspension members are provided with a lifting tab at the distal end that extends beyond the slider. An exemplary prior art head-gimbal assembly 60 of this form including a lift tab 51, is shown in FIG. 5. In FIG. 5, elements that correspond to elements in the assembly of FIG. 1, are identified with the same reference designations. In this form, the lifting tab 51 is used by the a head-loading mechanism of a spinstand to lower and lift suspension member 12 and, therefore, slider 10, during the loading and unloading operations. Lift tab 51 is typically located beyond slider 50, as an extension of the suspension member 12, but very close to slider 50. Like the head-gimbal assembly 15 of FIG. 1, the head-gimbal assembly 15 of FIG. 5 also includes electrical wires 16 disposed at the underside of the suspension member 12.
An example of a portion of a prior art head-loading mechanism of a spinstand incorporating head-gimbal assembly 15 of FIG. 5 is shown in FIG. 6. In FIG. 6, the arm 24 is laterally displaced (compared with the location of the corresponding arm in FIG. 2). Mounting portion 14 of the suspension member 12 is secured to cartridge 22, which in turn is secured to head-loading mechanism 20. Again, suspension member 12 is biased toward a magnetic disk 26 mounted on the spinstand. Suspension member 12 is engaged by arm 24 at tab 51 and its motion (and slider 10) relative to disk 26 is controlled by the vertical (Y) direction arm 24. In such a spinstand, the problem of damaging electrical wires 16 is eliminated, since arm 24 does not physically interact with the underside of head-gimbal assembly 15 in the area of electrical wires 16. However, this form of head loader has a different problem. That is, as cartridge 22 and head-gimbal assembly 60 are installed on the head loading mechanism 20, due to the initial angular orientation of suspension member 12, toward disk 26, the tab is relatively close to disk 26. As a consequence, that lifting arm 24 may not reliably engage lift tab 51.
For a particular type of head gimbal assembly, one of the above mentioned prior art head loading mechanisms may work better than another, but for certain types of heads each of them has one or more deficiencies, as described above. In older head and disk designs, the scratches and pits on the disk surface caused by the loading and unloading operations of such spinstands were within acceptable limits. However, as the head and disk technology progresses, there is an increasing need for higher precision and integrity of the head and disk components. Moreover, for certain types of head design, no prior art system is adequate.
Accordingly, it is an object of the invention to provide a head loading apparatus and method that minimizes damage to heads and disks during loading.
It is another object to provide a head loading apparatus and method that permits improved, minimal damaging loading without requiring special handling.